This invention relates to modular plastic conveyor belts, and more specifically to a radius type modular conveyor belt adapted to travel around lateral curves, and to a means for guiding the belt smoothly around curves.
U.S. Pat. Nos. 4,742,907 and 5,181,601 of KVP Systems, Inc. disclose modular plastic conveyor belts of the type with which this invention is concerned. Those conveyor belts are adapted to travel around lateral curves and have front and rear link ends or projections on each module, one set of which is slotted to allow collapse at the inner sides of curves. Both patents show guide members for guiding the belt around the outside of a curve, or at an intermediate position spaced outwardly from the inside of the curve, to promote smooth travel around the curve without bunching or vibration which might occur if the belt made contact with the stationary structure at the inside of the curve.
Robertson U.S. Pat. No. 5,224,587, shows a guide structure for generally the same type of modular conveyor belt, the guide being positioned to extend down from the center of the belt module. The guide structure of that patent, an inverted T-shape, was intended to act via the inner side of the T structure to both guide the belt and to hold the belt from pulling upwardly when travelling around a curve.
Other modular belts shown in patents have utilized guide members and hold down tabs of the general type described above. For example, see Horton U.S. Pat. No. 5,372,248.
Guide rollers have been used previously on other types of conveyors wherein different considerations and different structures were involved. See, as examples, U.S. Pat. Nos. 1,884,112, 3,117,668, 3,185,108, 3,214,007, 3,627,109, 3,788,447, 3,808,921, 3,854,575, 3,910,404, 3,951,256, 3,952,860, 4,179,025., 4,555,014, 4,645,070, 4,893,709, 5,076,422 and 5,174,436.
Of the above patents, U.S. Pat. No. 3,185,108 shows a pedestrian carrier which has a central roller to guide articulated platform segments, arcuate at their front edges, around very sharp U-turn curves. The solid conveyor platform segments, similar to those of a baggage conveyor in an airport baggage claim area, are very different from the rod-connected, interdigited plastic modules of this invention, which collapse together at the inner side around curves. Roller arrangements similar to that of U.S. Pat. No. 3,185,108 are also shown in other patents, but they are not shown in connection with modular belts in which virtually all longitudinal belt tension is carried in the outside edge of the belt during travel around curves, where belt guidance is critical.
U.S. Pat. Nos. 3,854,575 and 3,951,256 show radius type conveyor belts, generally of fixed radius and without linear travel, such as following a quarter-circle of travel and returning below over the same quarter-circle. Cone-shaped end rollers supported the generally fixed-radius belts. The belts in those patents were guided at their outer edges or inwardly thereof by rollers on vertical axes. In these types of belts different considerations are involved from those of a belt of the type with which this invention is concerned. Spiral conveyors have employed guide rollers, but again in a belt arrangement presenting very different considerations.
U.S. Pat. No. 4,645,070 shows a radius conveyor, but one which actually comprises a central chain with an attached wide top plate. In one embodiment the chain is guided by rollers on vertical axes.
It is an object of this invention to provide improved guiding and holding down structure for a modular plastic conveyor belt of the radius type, for guiding the belt in a smooth, low-friction and efficient manner around curves.